From patchwork Thu Dec 31 19:09:32 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Michael S. Tsirkin" X-Patchwork-Id: 7937641 Return-Path: X-Original-To: patchwork-xen-devel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id E2C28BEEE5 for ; Thu, 31 Dec 2015 19:11:32 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 1F62020465 for ; Thu, 31 Dec 2015 19:11:32 +0000 (UTC) Received: from lists.xen.org (lists.xenproject.org [50.57.142.19]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3FD3320115 for ; Thu, 31 Dec 2015 19:11:31 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=lists.xen.org) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1aEibX-0006ZR-L2; Thu, 31 Dec 2015 19:09:43 +0000 Received: from mail6.bemta5.messagelabs.com ([195.245.231.135]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1aEibW-0006YE-Of for xen-devel@lists.xenproject.org; Thu, 31 Dec 2015 19:09:42 +0000 Received: from [85.158.139.211] by server-13.bemta-5.messagelabs.com id C5/C2-06091-67D75865; Thu, 31 Dec 2015 19:09:42 +0000 X-Env-Sender: mst@redhat.com X-Msg-Ref: server-15.tower-206.messagelabs.com!1451588980!13161419!1 X-Originating-IP: [209.132.183.28] X-SpamReason: No, hits=0.0 required=7.0 tests=sa_preprocessor: VHJ1c3RlZCBJUDogMjA5LjEzMi4xODMuMjggPT4gNTQwNjQ=\n X-StarScan-Received: X-StarScan-Version: 7.35.1; banners=-,-,- X-VirusChecked: Checked Received: (qmail 34759 invoked from network); 31 Dec 2015 19:09:41 -0000 Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by server-15.tower-206.messagelabs.com with DHE-RSA-AES256-GCM-SHA384 encrypted SMTP; 31 Dec 2015 19:09:41 -0000 Received: from int-mx13.intmail.prod.int.phx2.redhat.com (int-mx13.intmail.prod.int.phx2.redhat.com [10.5.11.26]) by mx1.redhat.com (Postfix) with ESMTPS id 9176DC0B932D; Thu, 31 Dec 2015 19:09:39 +0000 (UTC) Received: from redhat.com (vpn1-7-165.ams2.redhat.com [10.36.7.165]) by int-mx13.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with SMTP id tBVJ9WhU004808; Thu, 31 Dec 2015 14:09:33 -0500 Date: Thu, 31 Dec 2015 21:09:32 +0200 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Message-ID: <1451572003-2440-30-git-send-email-mst@redhat.com> References: <1451572003-2440-1-git-send-email-mst@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1451572003-2440-1-git-send-email-mst@redhat.com> X-Mutt-Fcc: =sent X-Scanned-By: MIMEDefang 2.68 on 10.5.11.26 Cc: linux-mips@linux-mips.org, linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, Peter Zijlstra , Alexander Duyck , virtualization@lists.linux-foundation.org, "H. Peter Anvin" , sparclinux@vger.kernel.org, linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, Arnd Bergmann , x86@kernel.org, xen-devel@lists.xenproject.org, Ingo Molnar , linux-xtensa@linux-xtensa.org, user-mode-linux-devel@lists.sourceforge.net, Stefano Stabellini , adi-buildroot-devel@lists.sourceforge.net, Thomas Gleixner , linux-metag@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Andrew Cooper , linuxppc-dev@lists.ozlabs.org, David Miller Subject: [Xen-devel] [PATCH v2 29/32] Revert "virtio_ring: Update weak barriers to use dma_wmb/rmb" X-BeenThere: xen-devel@lists.xen.org X-Mailman-Version: 2.1.13 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP This reverts commit 9e1a27ea42691429e31f158cce6fc61bc79bb2e9. While that commit optimizes !CONFIG_SMP, it mixes up DMA and SMP concepts, making the code hard to figure out. A better way to optimize this is with the new __smp_XXX barriers. As a first step, go back to full rmb/wmb barriers for !SMP. We switch to __smp_XXX barriers in the next patch. Cc: Peter Zijlstra Cc: Alexander Duyck Signed-off-by: Michael S. Tsirkin --- include/linux/virtio_ring.h | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h index 8e50888..67e06fe 100644 --- a/include/linux/virtio_ring.h +++ b/include/linux/virtio_ring.h @@ -21,20 +21,19 @@ * actually quite cheap. */ +#ifdef CONFIG_SMP static inline void virtio_mb(bool weak_barriers) { -#ifdef CONFIG_SMP if (weak_barriers) smp_mb(); else -#endif mb(); } static inline void virtio_rmb(bool weak_barriers) { if (weak_barriers) - dma_rmb(); + smp_rmb(); else rmb(); } @@ -42,10 +41,26 @@ static inline void virtio_rmb(bool weak_barriers) static inline void virtio_wmb(bool weak_barriers) { if (weak_barriers) - dma_wmb(); + smp_wmb(); else wmb(); } +#else +static inline void virtio_mb(bool weak_barriers) +{ + mb(); +} + +static inline void virtio_rmb(bool weak_barriers) +{ + rmb(); +} + +static inline void virtio_wmb(bool weak_barriers) +{ + wmb(); +} +#endif struct virtio_device; struct virtqueue;